The two tone knobs on Fender's electric guitars are used for treble and bass adjustments respectively, and their principle of operation is to change the frequency response of the electric guitar by altering the value of the capacitors or inductors in the circuit, thus creating different tonal effects. Specifically, when the guitarist presses the tone button, the value of the capacitor or inductor in the circuit changes, which results in a change in the high and low frequency response of the electric guitar, thereby adjusting the guitar's tone. By adjusting the tone knob, you can make the electric guitar sound brighter and crisper or warmer and thicker.